1. Field of the Disclosure
This specification relates to a radio frequency identification (RFID) tag, and particularly, to a data persistence control apparatus for an RFID tag based on a flag technology.
2. Background of the Disclosure
Radio frequency identification (RFID) is a type of wireless (radio) communication scheme. The RFID has been developed for the purpose of transmitting and receiving a small amount of identification data via radio frequency signals. RFID technologies have been divided according to characteristics of applications to be applied.
The RFID technologies may be divided into an RFID technology using a high frequency band and an RFID technology using an ultrahigh frequency band according to frequency bands used. The RFID technologies may also be classified into a passive type, a semi-active type and an active type according to whether it is self-powered or not.
A communication units may generally be divided into a reader and a tag.
The reader may perform transmission and reception of the Radio Frequency (abbreviated as RF hereinafter) signal with the tag for reading information of the tag.
The tag may transmit stored information to the reader by modulating phase, amplitude or the like when the RF signal is received.
There is no unified international organization for regulating RFID technologies. Independent regulation and standards are subject to each nation which uses the RFID technology.
International standards for RFID technologies may include ISO/IEC, DASH 7, EPG global and the like, and be variously classified according to frequencies to be used for communications and usage purposes.
A flag technology of RFID-related technologies is a technology which is generally associated with a function of retaining (maintaining) response state information of a tag for a predetermined time when a communication distance between the reader and the tag is more than a predetermined distance, especially, when a plurality of tags are located within a radius of a communication-available distance of the reader. Here, the response state information of the tag refers to information indicating that tag which have already responded and transferred information to the reader, among a plurality of tags existing within an operating radius of the reader, selectively react with respect to a response request signal, sent by the reader, by retaining the tag response state as a predetermined value.
The flag technology is an essential technology when one reader reads a plurality of tags or when a plurality of readers read a plurality of tags. The associated description will be found in EPC global standards and the like.
Korean Publication Patent No. 10-2009-0073546, as the related art associated with the flag technology, discloses a data persistence (retention) control apparatus for an RFID tag. Here, a data storage unit and an amplification circuit play a role of a memory cell of a dynamic random access memory (DRAM). However, data loss is caused regardless of whether or not an electric power is supplied or after a predetermined time since power supplied. A data storage element which executes data storage is not required.
Also, the Publication Patent (10-2009-0073546) discloses that a capacity of a capacitor has to increase to extend a data persistence time. The increase in the capacity of the capacitor may cause an increase in an area of a semiconductor chip so as to generate extra costs. This may also cause electric power consumption, irrespective of operations relating to the flag technology.
U.S. Pat. No. 7,215,251 as another related art, discloses that a comparator is used as a component for implementing the flag technology. However, the comparator requires a constant current source which causes a continuous current consumption. With the continuous consumption of the constant current while the comparator is used, electric power loss may be caused.